An LTE system of which the specifications are formulated in 3GPP (3rd Generation Partnership Project), which is a project aiming to standardize a mobile communication system, supports downlink multi-antenna transmission (for example, see Non Patent Literature 1).
Along with recent expansion in communication demand, effective use of radio resources becomes more and more important even in communication technologies including LTE. Under such circumstances, there is a request for higher communication quality such as communication stability.